Bad news first — Doctor Who may be back on the air, but reality has yet to bless us with money emblazoned with Matt Smith's face. The good news? Thanks to the BBC, you can print out your very own David Tennant £10 notes. I'm pretty sure they're only legal tender on Gallifrey, so good luck with that.
What's the story behind this Time Lord tender? In the 2006 Doctor Who Christmas special "Runaway Bride," the Doctor creates a diversion by causing an ATM to malfunction with his sonic screwdriver. As the ATM discharges a flurry of cash, a crowd rushes over to grab the free money. For this scene, the show's art department created £10 and £20 pound notes bearing the faces of actor David Tennant and Doctor Who producer Phil Collinson, respectively.
Again, these are obviously not useable, unless you're the extremely bored Gods of Ragnarok who wish to tip your victims before you obliterate them.
Via the Doctor Who Facebook page and Zigmund, who noticed this on display at the British Museum's money exhibit.